Application for the benefaction of coal utilizing high volatile liquids as chemical comminutants

ABSTRACT

Mined coal of all grades contains numerous solid impurities such as slate, shale, and iron pyrites. The treatment of such coal with certain high vapor pressure chemical comminutants such as liquid anhydrous ammonia at - 33*C renders the coal into smaller particle sizes and separates it from its inherent impurities by means of the apparatus of the invention which includes a reactor receiving the coal to which is applied a chemical agent such as liquid anhydrous ammonia, and which separates the impurities from the coal and recovers the ammonia from both for reuse in the apparatus.

United States Patent Keller, Jr. et al.

Feb. 4, 1975 APPLICATION FOR THE BENEFACTION OF COAL UTILIZING HIGH VOLATILE LIQUIDS AS CHEMICAL COMMINUTANTS [75] Inventors: Douglas V. Keller, Jr.; Clay D.

Smith, both of Lafayette, NY.

[73] Assignee: Chemical Comminutions- International, Inc., Lafayette, NY.

[22] Filed: Aug. 22, 1972 [21] Appl. No.: 282,735

[52] U.S.Cl 241/1, 241/l5,241/18,

[51] Int. Cl. B02c 19/00 [58] Field of Search ..24l/14,16,1,15,18,

[56] References Cited UNITED STATES PATENTS 2,568,400 9/1951 Kearby 241/1 3,311,307 3/1967 Lopker 3,592,395 7/1971 Lockwood 24l/l8 RUN OF MINE COAL l2 Temperature, Chemistry and Industry, June 7, 1952, pgs. 502-508.

l.G.C Dryden, Action of Solvents on Coals at Low Temperatures, Fuel Vol. XXX, pgs. 3944 (1951).

L. Lazarov et al., Treatment of Coals with Sodium in Liquid Ammonia Solution, Fuel, Vol. XLVll, No. 5, pgs. 333-341, Sept. 1968.

Primary Examiner-Granville Y. Custer, Jr. Attorney, Agent, or Firm-Misegades, Douglas & Levy [57] ABSTRACT Mined coal of all grades contains numerous solid impurities such as slate, shale, and iron pyrites. The treatment of such coal with certain high vapor pressure chemical comminutants such as liquid anhydrous ammonia at 33C renders the coal into smaller particle sizes and separates it from its inherent impurities by means of the apparatus of the invention which includes a reactor receiving the coal to which is applied a chemical agent such as liquid anhydrous ammonia, and which separates the impurities from the coal and recovers the ammonia from both for reuse in the apparatus.

30 Claims, 8 Drawing Figures I I4 GAS CONDENSER REACTOR Lloum sp y LIQUID a COAL l6 AGITATION '0 PASM'ZE IMPACTOR 2 79 LES 94 PRESSURE EXCESS CONTROL GAS OVER- LIQUID 6 32 UNDERSIZE COAL OVERSIZE PARTICLES ROTOR FILTER uoum a UNDERSIZE COAL FILTER DRYER BELT LIOUID PLUS UNDERSIZE COAL,

R 76 D YER PRODUCT COAL I DRYER 62 BELTII 2 ETC. EXHAUST I GAS a CLASSIFIER ULTRA FILTER GAS- LIQUID RECOVERY l rw- PIHTLNIEUFEB 4mm 3.863.846

SHEET 10F 5 FIG. I

RUN OF MINE COAL l2 PRESSURE EXCESS GAS CONDENSER l K8 CONTROL GAS LIQUID SPRAY LIQUID a COAL l6 AGITATION OVER- SCREEN IMPACTOR 2o 78 PARTICLES 94 76 DRYER 9e LIQUID a /32 SCRAP UNDERSIZE COAL RoToR FILTER I OVERSIZE PARTICLES LIQUID a UNDERSIZE COAL 3s FILTER DRYER PRODUCT BELT COAL 5o LIQUID PLUS UNDERSIZE com.

64 72 1; DRYER GAS FLUID BELT4+2 ETc. U CLASS'F'ER ULTRA FILTER GAS-LIQUID k w 8 Q 3 I 6 F 8 L 3 m w o T 8 m N I! I w m w /mm 5 E VJ & +L F P 4 E m E M O S O Q E E 4 B O E E E 2 D I 0 I H E TI SCRAP I DRYER GAS-LIQUID RECOVERY SOLID CONVEYOR 4 -I2 4 mm U i TO GAS GAS EXHAUST LIQUID GA 5 RECOVERY LIQUID PLUS FINES PATENTEBFEB 41975 SHEET 3!]? 5 RUN OF MINE COAL 20cm PRESSURE CONTROL I EXCESS GAS Y REMOVAL GAS-LIOUID Q RECOVERY I PATENTED FEB H975 SHEET 0F 5 FIG4 FEED FROM REACTOR -4mm-O FEED TO TWO STAGE FILTER PATENTEDFEB'MBTS SHEET 5 OF 5 qhmgk h W N9 APPLICATION FOR THE BENEFACTION OF COAL UTILIZING HIGH VOLATILE LIQUIDS AS CHEMICAL COMMINUTANTS CROSS-REFERENCE TO RELATED APPLICATIONS The present invention relates to an apparatus which relates to the chemical reaction referred to in a copending patent application of R. G. Aldrich, D. V. Keller, Jr., and R. G. Sawyer, for Chemical Communication and Mining of Coal, filed Feb. I4, 1972, Ser. No. 232,324. No claim of rights is made under 35 U.S.C. ss 119,120 or 121.

FIELD OF THE lNVENTION The invention relates to apparatus to provide for the treatment of run of the mine" coal to be treated with high vapor pressure chemical agents, such as those that tend to reduce substantially the solid surface tensions effective between solid mixtures or combinations thereof, of compounds found in coal, resulting thereby in the subsequent separation and recovery of said chemical or physical agents. Examples of such agents are anhydrous ammonia used in liquid form.

The separate constituents derived from the coal may be used for commercial, industrial and utility uses and recovery of the liquid and gases reused in the process. The coal product is anhydrous and essentially freed from the undesirable impurities which are also anhydrous. A particular aspect of the invention relates to providing use of the impurities in their final form as being of relative commercial importance.

BACKGROUND OF THE INVENTION Natural coal as it is mined from its natural beds may contain more than 40 percent noncombustible constituents such as shale or slate, as well as generally high concentrations of undesirable minerals such as iron pyrites. The common process for the benefaction of such natural coal is to subject the run of the mine material to a hydro-benefaction treatment in which the coal is mechanically reduced in particle size and subjected to a series of water-chemical flotation treatments which remove substantial quantities of noncombustible rock and which render the coal a somewhat more efficient chemical and energy-producing material. Such hydrobenefaction types of treatment for coal do not provide a complete separation of the impurities from the coal in many cases. As a consequence, flotation or air classification procedures are inefficient often producing a coal product with considerably more than 5 percent impurities. The high concentration of impurities effects an increase in shipping costs, excessive corrosion during the energy conversion process, contamination during chemical usages, and excessive environmental pollution in the form of ash and the oxides of sulfur when the coal is oxidized. The product of such a process is also subject to loss in calorific value due to surface oxidation due to the high concentration of very fine particles generated in the process in contact with surface water.

According to recent disclosures, coal when subjected to certain high vapor pressure compounds such as anhydrous liquid ammonia (boiling point 33.4 C), is determined to be reduced in particle size by a process called chemical comminution. This size reduction effeet appears to change the particle size of only the coal and not other constituents of the coal bed materials which are undesirable in final usage of the coal. For example, slate, shale or iron pyrites are often found imbedded in a coal matrix as found in nature and when this composite is treated with the liquid, the particle size of the coal is rapidly and substantially reduced, whereas the undesirable slate, shale or iron pyrites are unaffected. The chemical properties of the coal are essentially unchanged, yet the coal is physically separated from the massive impurities. Also it is found that supernatent water in the coal has been removed.

SUMMARY OF THE INVENTION The apparatus of the invention as disclosed herein provides for the interaction of the high vapor pressure chemical comminutants, which are often hazardous when in bodily contact, with run of the mine coal such as to effect a physical separation of the coal from its impurities without the loss of the chemical comminutants and essentially complete recovery of the coal and impurities. The recovery of the chemical comminutants for reuse in subsequent cycles of chemical comminution establishes the economy of the apparatus and will tend to maintain environmental pollution to a minimum.

Accordingly, an object of the invention is to provide apparatus for a closed loop cycle in which coal is exposed to certain liquids which are herein identified as chemical comminutants, either by a continuous or with simple modifications, a batch system effecting a useful coal product, useful by-products, and a reusable chemical comminutant.

Another object ofthe invention is to expose the coal to the liquid or gas for some specific period of time under the conditions of a small variational mechanical stress, cyclical or otherwise, which is insufficient to cause mechanical failure of the untreated run of the mine coal, but large enough to improve the coal recovery efficiency. By mechanical failure is meant the physical structure collapse, or fracture of coal under an imposed stress.

A further object of the invention is the direct use of coal as it is received from the coal mining operation.

A more significant object of the invention is to effect a greater than percent separation of coal from the common impurities such as slate, shale and iron pyrites of the mine product utilizing a reducing atmosphere and an essentially anhydrous process. The calorific value of the coal is. essentially unchanged since air or water exposure is maintained to a minimum.

Another object of the invention is to effect improved separation of the impurities from coal without developing large quantities of coal aerosol which are a known health hazard.

A further object is to establish a separation of the individual by-product materials from the coal and each other for eventual use in industry.

A further object is to reduce significantly the air and water pollution generated by benefaction of coal.

A further object of the invention is to remove supernatent water from coal.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and advantages of the invention will become apparent upon full consideration of the following detailed description and accompanying drawings in which:

FIG. 1 shows a schematic block flow sheet diagram of the entire process which indicates the various material flows in accordance with a preferred embodiment of the invention;

FIG. 2 shows a schematic detail sketch and block diagram of the apparatus including the interaction of the reactor and three stages of size separation under a high vapor pressure liquid;

FIG. 3 shows a schematic enlarged detail diagram of the reactor and its salient features according to the preferred embodiment of the invention;

FIG. 4 shows in part a detailed diagram in vertical cross-section of the flow control from the reactor and the second stage of sizing the product;

FIG. 4A is a sectional view taken along line 4A-4A of FIG. 4;

FIG. 5 shows a vertically oriented schematic detailed diagram of the stage filter-dryer according to the preferred embodiment of the invention;

FIG. 5A is a cross-sectional view taken along lines 5A-5A of FIG. 5; and

FIG. 5B is a cross-sectional view taken along lines 5B5B of FIG. 5, each and all within the scope and purview of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Essentially anhydrous liquid ammonia having a boiling point of 33.4 C has been shown to act as one of what is to be identified herein as a more successful high vapor pressure chemical comminutant used in the benefaction of coal and, as such, serves as an excellent example for use in an explanation of the disclosed apparatus. The low boiling point and toxicity demonstrate the special requirements required of the apparatus which is capable of handling a large material flow char acteristic of the coal industry, e.g., in the range of hundreds of tons per hour. This example should not be construed as a limiting case for various chemical comminutants have been cited such as ethylamine, methylamine, including many others and mixtures thereof. Any combination of these chemical comminutants can be used in the disclosed apparatus with suitable modification for materials of construction and reaction temperature and rate adjustments.

Experimentation has quite conclusively shown that the reaction of coal with anhydrous ammonia requires a finite exposure time and the existance of a very mild mechanical stress in order to perform an efficient separation of the coal from its impurities. The extent of the exposure time is from seconds to large fractions of an hour; the extent of the mechanical stress which is always much less than the fracture stress of the untreated coal is dependent on the source of the coal. Bituminous coal from one Pittsburgh seam, for example, required nearly an hour for complete reaction; whereas that from another required only a few secondsexposure to disintegrate under its own stress. It should be noted that mechanical stresses which are large enough to cause the mechanical failure of untreated coal, such as those experienced in grinding mills or extensive impact caused by certain materials handling procedures,

should be considered as a gross disadvantage to the effectiveness of this separation process, since the impurities must be carried along to the density separation phase. For example, the optimum coal feed material for this process would be 100 percent of the coal with diameters greater than 12 mm, that is, no extensive mechanical fracture prior to chemical comminution, such that the impurities are removed at the earliest possible stage. Since modern mining procedures do not conform to this optimum, mechanical particle size reduction after the coal is received from the mine should be held to a minimum as is accomplished in the disclosed apparatus. Excessive water present in the run of the mine coal, such as coal from hydromining techniques, can represent an inefficiency in the process, water removal can be achieved by drying before the coal is added to the reactor or within the reactor itself. The water when added to the reactor along with the coal is for the most part removed by dissolution into the anhydrous ammonia establishing a water ammonia solution. This solution is then separated into its components water and anhydrous ammonia by a fractionation step which is common to the industry. Thus, supernatent water is readily removed from coal by use of the apparatus and method of the present invention.

Referring now to the drawings, there is shown in FIG. 1 a flow sheet diagram illustrating the generally descriptive phases and steps of the system according to a preferred embodiment of the invention; and FIG. 2 shows the apparatus of the reactor and filter assembly. The reactor 10 is of general and conventional construction forming an insulated tank and includes an entry means 12 to introduce run of the mine coal, a gas condenser l4, liquid spray means 16, a burden deflector 18, a screen 20 and an impactor 22. The reactor 10 is filled as shown with coal 24 and a liquid up to liquid level 26.

The reactor has exit means 30 that passes only 12mm to zero material from screen 20 through a valve 32, thence to a rotary screen 34 whichpasses 12mm material to liquid-solid separator means such as a continuous filter belt, rotary filter-dryer system 36 having a belt filter assembly 38 and a dryer portion assembly 40. The belt 42 moves in a clockwise direction and the liquid plus fines pass the belt into a space 46 and pass to a tube 48 to a container 50. Roller element seals 54,56,58, are for separating and aiding the drying of the reactants.

Oversize reactant particles that do not pass into space 46 may pass into the dryer portion where they are exposed to hot ammonia gas for drying. The gas passes to space 60 then through a tube 62 into a gas exhaust chamber 64. Oversized particles pass to a further conveyor belt and which then passes the solid to a fluid classifier 72. Gas is recovered in gas-liquid recovery means 66.

From the reactor 10, oversized particles of plus 12mm size pass through oversize exit means 76 to an elevator 78, thence to a dryer 80 and pass to a scrap container 82. The liquid comminutant which was introduced by the liquid spray !6 at about 33.4 C interacts with the run of the mine coal at ambient temperature causing a quantity of the liquid to boil. As shown in FIG. 3 described below, some of the gas is recovered by the condensers l4 and the gas, not thereby condensed, is removed from the reactor 10 by excess gas removal means 81 an passed to recovery means 66.

Pressure control means 88 insures that the rate of gas removal is such that the reactant gas does not escape from entry means 12 into the atmosphere. The anhydrous liquid interacts with the relatively hot coal by excessive boiling and vaporization of the ammonia resulting in a high pressure over the coal at the entry means 12, FIG. 3. Recovery of this gas is achieved by removal of the excess ammonia gas. This may be accomplished by a pressure sensor at entry means 12, such as in the gas recovery pressure control means 88 (FIG. 3), which at excessive pressure removes excess gas by pump or gas removal means 81.

The particles from the rotary screen 34 that are sized between l2+4mm pass from the pipe 90 to a lift and conveyor means 92 to a dryer 94, and separation between the liquid and scrap is made so that scrap is collected in scrap unit 96 and the liquid-gas is passed to a gas recovery unit 66.

The description of FIG. 2 has been set out above and, for purposes of understanding FIG. 1, similar and corresponding sets of reference nuemrals are applied throughout to both FIGS. 1 and 3, among other figures wherein similar elements or components are given corresponding reference numerals to those described in FIG. 2.

The reactor in order to be applicable in all situations of varying feed stock coal is provided with control means for the reactor that has at least three essential requirements: (1) an ability to recover the massive amount of ammonia gas generated during boiling as the mine run coal is cooled with the liquid ammonia to 33 C from ambient conditions using either a saturating spray or liquid immersion; (2) a dwell time exposure to an essentially anhydrous ammonia bath in an insulated tank for periods variable to at least one hour under conditions of a reciprocating mild mechanical stress; and (3) separation of the large masses, usually greater than 12mm diameter impurities, from the useful product coal which is normally less than 1.5 mm diameter provided the exposure was adequate. Requirement (2) is accomplished by a proper balance of feed rate of run of mine coal to the reactor, the exhaust rate of the treated coal from the reactor, and bed of reacting coal size (depth and diameter). Assuming equal input and outputs of coal, the depth of coal bed in the reactor establishes the desired dwell time" while the bed load (e.g., mass) provides a portion of the mild mechanical stress. An added mild mechanical stress is provided with impactors 22 for improved efficiencies. The reactor stage illustrated in FIG. 3 provides these requirements in an optimum configuration. Mined coal to be used in the reactor is normally 40cm in diameter down to micron particle size mixed with slate, shale and pyrites and other impurities. This feed material is continuously added to the chamber in reactor 10 through entry means 12 and exposed to a spray means 16 of anhydrous ammonia forming a mixed mass of coal and liquid below or at 33 C. The ammonia gas evaporated during the temperature reduction of the coal from ambient to 3 3 C is recondensed on finned chiller elements forming the gas condenser 14 located in the top portion of the reactor, and the liquid product is permitted to drop and reenter the bed in the reactor. A standard refrigeration cycle cools the coils of the gas condenser 14 to a temperature well below the condensation point of the ammonia gas. The ammonia gas pressure at the coal entrant point 12 in the reactor 10 is maintained slightly below atmospheric pressure to insure that no gas is lost during the coal cooling procedure. This is accomplished with a pressure control 88 at the throat of the vessel which controls a conventional evacuation blower at the top of the vessel. The excess gas is transported to the gas recovery station 66. The location of the condenser 14 in the top of the reactor 10 is by convience since all of the gas could be removed by an exit pipe, recondensed and returned to the system by the sprays.

The coal bed 24 in the reactor 10 is a mixture of unreacted coal, coal at various stages of size disintegration, large masses of the impurity material and liquid ammonia. The large masses of impurities which have not disintegrated provide the mild mechanical stresses which are necessary for efficient contaminant separation, bed vibration, screen clearing and ultimate effective separation of the 12mm to zero and the larger than 12mm diameter material. A gas driven impactor 22 placed in the vicinity of the 12mm screen 20 creates mild shock waves in the bed by injecting bursts of relatively hot ammonia gas into the bed and/or just below the screen to cause bubble cavitation and the resulting shock wave upon the condensation of the gas. Control of the quantity of gas, e.g., intensity of the shock wave, and the pulse length to any frequency provides controllable screen and bed agitation. The agitation permits the desired mechanical stress during reaction, screen separation of the 12mm to zero particles, the removal of the 12mm scrap and destruction of mechanical bridges in thebed. Other mechanical means of bed agitation might also serve this purpose. A burden deflector 18 or deflectors, mounted such as not to interrupt the flow of the 12mm particles, insures that all of the charge passes across the 12mm screen. The larger than 12mm material is transported to an elevator 78 in an exit pipe and is removed from the process by depositing in a mechanical conveyor 78 for removal to a rotary dryer 94 for gas recovery and the solid to crap 96. A conventional rotary kiln or screen might be used to remove the absorbed liquid ammonia. In the cases of coals from several sources, material of particle size greater than 4 mm could be considered scrap; therefore, either the 12mm screen could be reduced to 4mm, or a second screen added below the 12mm screen would effect a more refined separation.

In the case where only the 12mm screen was used, the 1 2mm to zero material which passes the screen 20 is collected in the bottom of the reactor for conveyance to the next stage of size separation. Clearly, no severe modifications of this apparatus are necessary to use the reactor in a high pressure mode of a batch process since after filling of the system, a cap should be provided at the filling port. After subsequent reaction and pressure adjustment back to atmospheric pressure, the processingof material separation continues. Furthermore, the 12mm to zero particles could, less efficiently, be mechanically conveyed in a manner similar to the +l2mm material for kiln drying and ammonia gas separation. A more efficient process is to transport the liquid in a flow with the l2mm to zero material to a rotor case screen 34, as illustrated in FIG. 4. The mixture, l2mm to zero solid and liquid, as emitted from the reactor 10, is fed through a high capacitance orifice directly to the surface of rotating screen 34 with, for example, 4mm hole diameters such that the anhydrous liquid ammonia and solids 4mm to zero pass through the screen, while the +4mm to l2mm particles are retained on the surface of the screen. The particles on the screen are, in rotation, washed with pure liquid ammonia and then scraper into the discharge tube by a scraper 112. Since the oversized particles are in some cases over 90 percent non-coal products, this material is sent to the rotary kiln dryer 94 used for the +l2mm scrap, and the ammonia gas is also recovered in recovery 66, as shown in FIG. 1.

The rotary screen 34 of FIG. 4 is disposed within an insulated housing 116, and the screen turns on a sealed load bearing 118 for supporting an exit pipe 90 described above. The screen is cleaned by means of a scraper 112. The screen turns on an axis (FIG. 4A) coaxial with the vertical portion of orifice 110. Similarly to bearings 118, a bearing seal 124 and a driver 126 with a bearing seal 128 are provided as shown in FIG. 4. Basket screen 34 is rotated by drive 126 and causes material deposited by orifice 110 to pass the spray heads 130 and then dislodged by stationary scraper 112.

Other than performing an essential separation, the continuous rotary filter 34 whether in the physical orientation shown or mounted horizontally (not shown), also performsa second important function. That is, the regulation of the flow from the reactor such that the complete liquid ammonia head in the reactor system is not dissipated. The liquid pressure exiting from the rotating filter is very nearly atmospheric, whereas that en tering the system is at the head pressure of the reactor. The atmosphere within the entire filter is anhydrous ammonia gas. All components, gaskets, bearings, seals and lubricants, some of which are shown in FIGS. 3, 4 and 5, must therefore be compatible with the atmosphere such as is consistent with those requirements as clearly described in the ammonia industry. In the event a two-stage screen (not shown) is used in the reactor and the output is 4mm 0, the rotor filter is unnecessary.

The 4mm to zero material in anhydrous liquid ammonia mixture can, at this point, be separated by a simple filter technique, the solid being dried in a kiln for ammonia gas recovery and dry sized for final separation of the coal and impurities. more efficiently, the mixture can be placed in the continuous filter-dryer 36, shown in FIG. 5. The 4mm to zero material in anhydrous liquid ammonia is fed in a tubulent fashion onto a continuous belt screen 42 with, for example, 2mm diameter openings such that the liquid and undersized material passes through the screen to an exhaust. The liquid ammonia and fine material is fed in a turbulent fashion to the bed filter as illustrated in FIG. 2, i.e., by position in the system. If this slurry were permitted to stagnate the fines would settle out and block the flow. The continuous belt moves at a rate controlled by a solid bed sensor 140 of a mechanical deflector type, which establishes a depth of filter bed material 144. The belt illustrated moves from left to right and after the elastic rotor seal 56 at the center, the bed is exposed to hot anhydrous ammonia gas which enters through openings 146 from above the bed and exits through the bed at exit 200 to tube 62 such as to dry the bed completely. The distance between the rotor seals 56,58 is such as to permit the bed material complete drying. The dry residue 4 2mm coal and impurities is then mechanically removed from the screen to a conveyor belt for density classification, i.e., the separation of coal from impurities. The filter belt 42 is then cleaned by mechanical means 50 and/or air brushing means 50 and then returned to the liquid chamber for further liquid filtering. Two elastic rotor seals 54, 56 essentially isolate the liquid chamber from the rest of the system.

The two-stage filter dryer 36 shows the rotary element seals 54, 56, 58 in FIG. 5 and FIG. 5A shows the details of the elastic rotor seal 54, the belt 42 and its support 152. Feed stock entry 154 is shown in FIG. 5B and the various supports, namely, slide supports 156, 156 and roller support 158. The configuration of the rotor seals and a mask 160, 160 for the seals 54 and 58, respectively, in FIG. 5 is apparent, and the roller seals 54, 56, 58 are each mounted on a spring bias arrangement 162, 162 urging the rotor seal into engagement with the bed 144.

The undersized particles and excess anhydrous liquid ammonia are removed from the chamber immediately below the belt through tube and used as feed stock for a second, third, etc., filter-dryer unit which would provide as many size fractions as was desirable. For example, the product of the filter-dryer 36 just described would be essentially 4 to +2mm. Such a product, a mixture of coal, slate or shale and pyrites, is an excellent feed stock for fluid density classification such as a fluid bed separation or cyclone separation, since the diameters of all components are very nearly the same and the density of the coal is about 1.1 gms/cc as compared to the rock which is in the range of 2.3 gms/cc. Pyrites has a density of about 5.6 gms/cc and can readily be separated from the rock and coal. Clearly, the range of particle sizes which can be tolerated in one or more stages of filtration for an acceptable product from gas classification are dependent on the chemistry and morphology of the bed coal and the exact specific gravities of the components which are used in the process. The addition of one or more washing sections or additional dryers to the filter-dryer component may be provided within the degree of reasonableness shown and described above. It has been established that liquid bed screening is much more efficient for the separation of small particle size materials than are in air screening techniques, e.g., problemsof dusting and crushing are essentially eliminated.

Throughout the three main stages, i.e., reactor 10, preliminary filtering 34 and final filtering 36, a minimum of liquid ammonia has been transported to the drying stage which constitutes an efficiency in this system. As a consequence, after final filtration of the liquid to remove the ultra fine particles, it can be returned to the cycle at the reactor stage. The residue gases from the three stages and final drying processes can be used as such for filtrate drying or submitted to a typical mechanical or absorption refrigeration cycle for liquification, purification and readmittance to the cycle.

The coal after treatment exists in particle sizes less than 2mm; all particles larger are essentially scrap. The coal is sized to within rather narrow size ranges, dried and subjected to ammonia gas classification by welletablished fluid bed or cyclone separation techniques to effect the final separation of coal from the other impurities. The coal at the conclusion of this stage has not been exposed to an oxidizing atmosphere which would tend to reduce its calorific value to some degree by surface absorption process. The particle size of the product is in the range 2 to 0.2mm and is essentially free from impurities.

The residue from the benefaction process consists of sized slate, shale, iron pyrites and other stone materials of unique specific gravity. Density separation of the materials can be used to isolate, for example, iron pyrites as a source material for iron and/or sulfur production or separation of the slate for processing and use in the building trades industry.

As will be apparent from the foregoing, the present invention provides novel means for the separation of certain impurities from natural coal. There are also provided a number of advantages in operation over the prior benefaction processes for the removal of these impurities. The apparatus is simple and comparatively inexpensive and non-complex in operation. Supernatent water is readily removed from coal by use of the apparatus and method of the present invention.

It should be recognized that the apparatus illustrated in the drawings is essentially diagrammatic and that it is not intended to show all of the well-known details of construction which would be required in the building of apparatus for carrying out the invention. The invention has been described above with respect to the benefaction of bituminous coal with anhydrous liquid ammonia. Nevertheless, it will be understood that substantially identical apparatus may be employed in the benefaction of other grades of coal with other high vapor pressure chemical comminutants for the purpose of removing the natural impurities.

Additional embodiments of the invention in this specification will occur to others and therefore it is intended that the scope of the invention be limited only by the appended claims and not by the embodiment described hereinabove. Accordingly, reference should be made to the following claims in determining the full scope of the invention.

What is claimed is:

1. Apparatus for comminuting coal comprising:

a reactor containing coal essentially submerged in a liquid chemical comminutant for producing reactants, such as impurity materials and product coal, the reactor including (1) means to provide a small variational mechanical stress on the coal by the comminutant, and (2) means to provide at least a partial separation of the impurity materials from the coal without generating environmental pollutants or physical hazards.

2. The invention according to claim 1 wherein said reactor includes means for applying the liquid comminutant at a pressure above that of atmospheric.

3. The invention according to claim 1 wherein said coal is run of the mine coal.

4. The invention according to claim 1 wherein said liquid chemical comminutant has gaseous and liquid phases, the reactor is connected to means recovering the liquid chemical comminutant in its gaseous and liquid phases, means processing the gaseous phase into the liquid phase, means feeding the liquid phase to the reactor to form a closed loop, and a continuous rotary filter-dryer means also disposed in said loop and is connected to the reactor as a second stage to provide removal of all particle sizes larger than l.5mm essentially without uncontrolled loss of the liquid in said closed loo 5 The invention of claim 1 in which the reactor has an outlet for the separated coal connected to a continuous rotary filter-dryer means to separate undersized particles and liquid and oversized particles.

6. The invention according to claim 1 wherein the reactor has an outlet for the separated coal connected to a ganged continuous belt filter-dryer means to provide particle size separation.

7. The invention according to claim 1 in which the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and recovering means provides essentially total recovery of the high vapor pressure chemical comminutant throughout the apparatus.

8. The invention according to claim 1 in which said reactor has an outlet for the separated impurity materials.

9. The invention according to claim 3 in which a continuous belt rotary filter-dryer means is connected to receive the reactants from the reactor for separation of the undersized particles and liquid and filter bed drying of the oversized particles in one continuous operation.

10. The invention according to claim 2 wherein said reactor has an outlet connected to a ganged continuous belt filter means to provide particle size separation.

11. The invention according to claim 7 wherein said reactor has an outlet connected to a ganged continuous belt dryer means and includes means to provide particle size separation.

12. The invention according to claim 4 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and the recovering means provides essentially total recovery of the high vapor pressure chemical comminutant throughout the apparatus.

13. The invention according to claim 5 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and the recovering means provides essentially total recovery of the high vapor pressure chemical comminutant throughout the apparatus.

14. The invention according to claim 4 in which said reactor has an outlet for the separated impurity materials.

15. The invention according to claim 5 in which said reactor has an outlet for the separated impurity materials.

16. Method for comminuting coal comprising:

reacting coal essentially submerged in a liquid chemical comminutant in a reactor to produce reactants such as impurity materials and product coal, applying a small variational mechanical stress on the coal and (2) partially separating the reactants from the coal.

17. The invention according to claim 16 wherein said step of reacting includes processing the coal with the liquid comminutant at a pressure above that of atmospheric.

18. The invention according to claim 16 wherein said coal in the reactor is run of the mine coal from which supernatant water in the coal has been removed.

19. The invention according to claim 16 wherein subsequent to the step of partially separating reactants from the coal is the step of removing all the particle sizes larger than 1.5mm without uncontrolled loss of the liquid by a rotary filter-dryer means.

20. The invention of claim 17 which includes the step of receiving the reactants from the reactor by a continuous belt rotary filter-dryer to separate the undersized particles and liquid and drying of the over-sized particles in one continuous operation.

21. The invention according to claim 16 wherein is the further step of separating and drying by use of a ganged continuous belt means.

22. The invention according to claim 16 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant, and a recovering step for essentially total recovery of the high vapor pressure chemical comminutant.

23. The invention according to claim 16 in which after the step of reacting is the further step of recovering of impurity materialo naturally found in said coal.

24. The invention according to claim 18 which includes the step of separating of the undersized particles and liquid, and drying of the oversized particles.

25. The invention according to claim 22 wherein is the further step of separating and filter-drying by use of a ganged continuous belt means.

26. The invention according to claim 23 wherein is the further step of separating and filter-drying by use of a ganged continuous belt means.

27. The invention according to claim 19 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and a recovering step for essentially total recovery of the high vapor pressure chemical comminutant.

28. The invention according to claim 20 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and a recovering step for essentially total recovery of the high vapor pressure chemical comminutant.

29. The invention according to claim 19 in which after the step of reacting is the further step of recovering of impurity materials.

30. The invention according to claim 20 in which after the step of reacting is the further step of recovering of impurity materials. 

2. The invention according to claim 1 wherein said reactor includes means for applying the liquid comminutant at a pressure above that of atmospheric.
 3. The invention according to claim 1 wherein said coal is run of the mine coal.
 4. The invention according to claim 1 wherein said liquid chemical comminutant has gaseous and liquid phases, the reactor is connected to means recovering The liquid chemical comminutant in its gaseous and liquid phases, means processing the gaseous phase into the liquid phase, means feeding the liquid phase to the reactor to form a closed loop, and a continuous rotary filter-dryer means also disposed in said loop and is connected to the reactor as a second stage to provide removal of all particle sizes larger than 1.5mm essentially without uncontrolled loss of the liquid in said closed loop.
 5. The invention of claim 1 in which the reactor has an outlet for the separated coal connected to a continuous rotary filter-dryer means to separate undersized particles and liquid and oversized particles.
 6. The invention according to claim 1 wherein the reactor has an outlet for the separated coal connected to a ganged continuous belt filter-dryer means to provide particle size separation.
 7. The invention according to claim 1 in which the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and recovering means provides essentially total recovery of the high vapor pressure chemical comminutant throughout the apparatus.
 8. The invention according to claim 1 in which said reactor has an outlet for the separated impurity materials.
 9. The invention according to claim 3 in which a continuous belt rotary filter-dryer means is connected to receive the reactants from the reactor for separation of the undersized particles and liquid and filter bed drying of the oversized particles in one continuous operation.
 10. The invention according to claim 2 wherein said reactor has an outlet connected to a ganged continuous belt filter means to provide particle size separation.
 11. The invention according to claim 7 wherein said reactor has an outlet connected to a ganged continuous belt dryer means and includes means to provide particle size separation.
 12. The invention according to claim 4 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and the recovering means provides essentially total recovery of the high vapor pressure chemical comminutant throughout the apparatus.
 13. The invention according to claim 5 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and the recovering means provides essentially total recovery of the high vapor pressure chemical comminutant throughout the apparatus.
 14. The invention according to claim 4 in which said reactor has an outlet for the separated impurity materials.
 15. The invention according to claim 5 in which said reactor has an outlet for the separated impurity materials.
 16. Method for comminuting coal comprising: reacting coal essentially submerged in a liquid chemical comminutant in a reactor to produce reactants such as impurity materials and product coal, applying a small variational mechanical stress on the coal and (2) partially separating the reactants from the coal.
 17. The invention according to claim 16 wherein said step of reacting includes processing the coal with the liquid comminutant at a pressure above that of atmospheric.
 18. The invention according to claim 16 wherein said coal in the reactor is run of the mine coal from which supernatant water in the coal has been removed.
 19. The invention according to claim 16 wherein subsequent to the step of partially separating reactants from the coal is the step of removing all the particle sizes larger than 1.5mm without uncontrolled loss of the liquid by a rotary filter-dryer means.
 20. The invention of claim 17 which includes the step of receiving the reactants from the reactor by a continuous belt rotary filter-dryer to separate the undersized particles and liquid and drying of the over-sized particles in one continuous operation.
 21. The invention according to claim 16 wherein is the further step of separating and drying by use of a ganged continuous belt means.
 22. The invention according to claim 16 whereIn the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant, and a recovering step for essentially total recovery of the high vapor pressure chemical comminutant.
 23. The invention according to claim 16 in which after the step of reacting is the further step of recovering of impurity materialo naturally found in said coal.
 24. The invention according to claim 18 which includes the step of separating of the undersized particles and liquid, and drying of the oversized particles.
 25. The invention according to claim 22 wherein is the further step of separating and filter-drying by use of a ganged continuous belt means.
 26. The invention according to claim 23 wherein is the further step of separating and filter-drying by use of a ganged continuous belt means.
 27. The invention according to claim 19 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and a recovering step for essentially total recovery of the high vapor pressure chemical comminutant.
 28. The invention according to claim 20 wherein the liquid chemical comminutant in the reactor is a high vapor pressure chemical comminutant and a recovering step for essentially total recovery of the high vapor pressure chemical comminutant.
 29. The invention according to claim 19 in which after the step of reacting is the further step of recovering of impurity materials.
 30. The invention according to claim 20 in which after the step of reacting is the further step of recovering of impurity materials. 